Yet Cruz jumped into a confrontation with Heinzman last week, welcoming a spat with her about a source of his campaign funds.

The tense exchange was remarkable not only for Cruz's willingness to leap into the fray, but also for a new fissure it seemed to reveal between him and his opponent.

Cruz has insistently framed the race as a battle between “the moderate establishment,” embodied by Dewhurst, and a “tidal wave” of tea party conservatives, whom he represents.

Yet Heinzman was berating Cruz precisely because she wasn't buying his claim to conservatism, particularly on social issues. And to prove her point, she needled Cruz to return contributions from one person in particular: Peter Thiel.

A billionaire hedge-fund manager in Silicon Valley, Thiel is also a gay libertarian who supports same-sex marriage.

“I understand that y'all are passionate for Dewhurst, and I appreciate your passion,” Cruz told her.

“I'm passionate for marriage,” Heinzman said.

“And when has Dewhurst ever stuck his neck out and supported ... ”

“Absolutely,” she interrupted. “He has a proven record. He voted (for) that family amendment.”

“I don't disagree that he didn't kill it,” Cruz said, apparently in reference to the Legislature's passage in 2005 of an amendment banning same-sex marriage. “Let me encourage you to read something.”

“I will encourage you to send back a quarter of a million dollars,” Heinzman said.

Thiel contributed about $251,000 to Cruz's 2009 bid for attorney general. (A former state solicitor general, Cruz dropped out when Greg Abbott decided to run for re-election.)

Thiel tossed more money into Cruz's corner last year for the Senate race, $7,400 so far.

Locking horns with Heinzman, Cruz seemed to assert the cash would not sway his opposition to same-sex marriage.

“They can expect whatever they want,” he told her. “My positions are absolutely clear and they have never altered.”

But the encounter underscored a split within the tea party, Cruz's supposed base, whose supporters occupy a notoriously big tent.

While some are social conservatives, others are secular-minded libertarians concerned solely with fiscal issues.

In a study last year by the Pew Forum on Religion and Public Life, nearly half of tea partiers said they had no strong opinion about the religious right, while one in 10 said they disagreed with religious conservatism.

A 2010 poll, meanwhile, found that nearly 40 percent of tea partiers described themselves as evangelical Christians.

Cruz barely touched on social issues in a speech at the convention.

Dewhurst, however, went all in.

“Like so many of you, as a believer in the Lord Jesus Christ, I am offended by this administration, the most secular administration in my lifetime,” he said. “I don't think anyone in Washington actually thinks about the words, ‘Thou shalt love thy God with all thy heart, with all thy soul and with all thy mind.'”

Dewhurst added that “most importantly,” he would “stop this administration from trampling on our family values and our religious freedoms.”

The activists at the convention clearly favored Cruz. But could the rigid views of social conservatives like Heinzman give the lieutenant governor an unexpected edge in the July 31 runoff?

With the tea party such a mixed bag, that's another node of uncertainty in a race already boiling with it.